A litigator is calling for the SEC to look into Goldman Sachs' upgrade of Tesla stock preceding the launch of its stock offering.

Goldman Sachs' upgrade of Tesla stock, just hours before the electric car maker revealed it also had tapped the investment bank to underwrite a $1.7 billion stock sale, already has drawn plenty of critics.

"To start investigating, all the SEC has to do is have a belief that something amiss may have happened," said Andrew Stoltmann, a Chicago lawyer who has pursued dozens of arbitration actions and lawsuits against large financial services firms.

And Stoltmann believes the commission has enough to go on, simply in the timing of the stock sale announcement.

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Elon Musk

Early Wednesday, Goldman Sachs revealed a bullish upgrade of Tesla stock, to "buy" from "neutral," calling for 22 percent upside and a six-month price target of $250. The bank said it doesn't "believe Tesla shares are fully capturing the company's disruptive potential."

Tesla shares rose at the open Wednesday. But after the market closed, Tesla announced its stock offering would be co-led by Goldman, and the carmaker's shares gave back gains, falling into the red in after-the-bell trading. The shares were up more than 2 percent late Thursday.

Big banks are required to keep a "Chinese wall" separating research divisions from banking teams.

"It's uncommon, but probably not unusual," said one industry lawyer who declined to be named.

The lawyer said that, potentially, the bank's independence between research and banking arms is what ultimately led to the timing surrounding the upgrade and subsequent offering. Further, the bank has a yearslong relationship with Elon Musk's automaker; it isn't as if Tesla became a Goldman client this Wednesday.